@QueenCandy23,
The response is similar if you're in Canada.
1. get a lawyer
2. child support is divided by the number of children the person has judgment orders for - so if he's already paying for 4, he'd be paying for 5 - and your daughter would get 1/5 of the total
3. your ex will not have any responsibility for your future husband's child
__________
Based on the numbers you've provided, if he was determined to be able to pay $1300 in the past, 1/5 would be less than the $300 he sent on the months he did send money. Looks like he sent you roughly the same amount he was paying for the other 4, even though he hadn't been ordered to.
If he's not working, he's not likely to be given the same assessment as in the past. (at least not in Canada)